Análise das estratégias de movimento adotadas durante a realização de manuseio de carga.
Resumen
Despite recent technological advances, occupational activities of manual nature are still
essential in many sectors and industries. Such activities impose risky conditions, which
are inherent to its nature and can be responsible for musculoskeletal injuries. In
addiction, the complexity and the interaction of risk factors, many still not
comprehended, that act together during the performance of manual material handlings
confer challenges and stimulations to the preventive approach. In this way, two main
studies (Studies I and II) and two unfolding studies had been carried through. The main
studies contextualized the hamstrings flexibility and its influence on the performance of
occupational tasks. The objectives of Study I had been to compare the results of two
clinical tests used to evaluate hamstrings flexibility and to evaluate the reliability of the
photogrammetric procedure adopted for the analysis. The fingertip-to-floor test and
straight leg raise test were applied in 35 healthy male subjects. Based on tests results,
subjects were divided into two groups: normal and reduced flexibility. Superficial
anatomical landmarks were fixed on bony references by means of manual palpation in
order to permit the tracing of the hip, thoracic-lumbar, leg, knee and tibio-tarsal angles.
The student t test was applied to evaluate the differences between the two groups, for
each variable. Findings showed that hip angle was significant lower at the reduced
flexibility group and that the straight leg raise test was more sensible for detecting
subjects with reduced flexibility. The aim of Study II was to evaluate the influence of
hamstrings flexibility on the movement strategy of the trunk and pelvis adopted by
healthy subjects during the performance of the manual handling. Subjects were divided
into two groups, based on the straight leg raise test. A JVC digital camera with a
sampling of 50 frames/second and positioned perpendicularly to the sagittal plane of the
subjects was used to register the activity. The cross-correlation coefficient was used to
quantify movement patterns relationship between groups, and the student t test applied
to the movement variables in order to determine differences between groups. The results
had demonstrated that subjects with reduced flexibility used a lesser pelvic amplitude
and bigger amplitudes of the trunk during handling. Still, subjects with reduced
flexibility adopted a retroverted movement of the pelvis, without great alterations during
the activity. The unfolding studies contextualized the comparison of the strategies
adopted by subjects with experience in load handling activities and inexperienced
individuals. The Study III had as objective to evaluate the manual handling performed
by 16 experienced subjects and 15 inexperienced ones. It was used a flexible
electrogoniometer to measure trunk movements and the University of Michigan 3D
software to estimate the intradiscal compression in L5/S1 during the handling. The
normalized movement patterns were evaluated and the coefficient of variation was
applied to quantify the variability of this movement. The student t test determined the
differences between variables. Results pointed out to great variability of adopted
postures. Smaller amplitudes of flexion had been found, but bigger amplitudes of trunk
extension when the loads were deposited, respectively, in low and high surfaces for
experienced individuals. Experienced subjects presented lower intradiscal compression
during box deposition and the lowering task was characterized by the highest intradiscal
compression. Study IV aimed to compare manual handling strategies adopted by
experienced and inexperienced subjects with relation to the positioning of the feet and
trunk during lowering and inclination of the box during lowering and lifting activities.
Ten experienced workers and 10 subjects without professional experience with the
handling activity had been selected. The manual handling carried out between different
heights was filmed. By means of one edition software, the images referring to the
instant of 50% of the task had been selected and used to classify the postures and to
measure the inclination of the box. An ANOVA with 3 factors was used to evaluate the
inclination of the box with relation to the experience, handled load and type of handling
(lifting and lowering). The results had indicated that subjects with professional
experience adopted strategies characterized by biggest inclination of the box and
adoption of balanced postures of the trunk, with widening of the support base.
Professional experience determined the adoption of different movement strategies, when
compared to inexperienced ones, in response to task conditions. However, other studies
are suggested in order to determine if such strategies were protective or risky ones. The
results presented in this dissertation raise the hypothesis that hamstrings flexibility is a
risk factor for the increase of trunk overload, during the performance of manual material
handling.